The molecular mechanisms by which troponin and tropomyosin regulate the interaction of actin and myosin in skeletal and cardiac muscle will be investigated, involving a detailed study of the changes in structure and interactions among the troponin subunits and the other thin filament proteins, actin and tropomyosin. This will be approached by studying a) the effect of metals on the structure of skeletal and cardiac TnC and their proteolytic fragments, and b) the transfer of metal-induced structural information to proteins forming complexes with TnC. The major experimental tools for these studies will be optical and magnetic spectroscopy.